↑ OED, s.v. "year", entry 2.b.: "transf. Applied to a very long period or cycle (in chronology or mythology, or vaguely in poetic use)."
↑ Ziggelaar, A. (1983). "The Papal Bull of 1582 Promulgating a Reform of the Calendar". In Coyne, Hoskin, Pedersen (eds), Gregorian Reform of the Calendar: Proceedings of the Vatican Conference to Commemorate its 400th Anniversary. Vatican City: Pontifical Academy of Sciences, Specolo Vaticano, p. 223
↑ Claudius Ptolemy, tr. G. J. Toomer, Ptolemy's Almagest, 1998, Princeton University Press, p. 139. Hipparchus stated that the "solar year ... contains 365 days, plus a fraction which is less than 1/4 by about 1/300th of the sum of one day and night".
↑ Richards, E.G. (2013). “Calendars”. Trong Urban, S.E.; Seidelmann, P.K. Explanatory Supplement to the Astronomical Almanac (PDF) (ấn bản 3). Mill Valley, CA: University Science Books. tr. 585, 590. ISBN978-1-891389-85-6. Richards does not explicitly state Anno Domini is the worldwide standard, but does state on page 585 the Gregorian calendar is used throughout the world for secular purposes; the Gregorian calendar is used with the Anno Domini era.
